Chemiluminescence quantum yield in permanganate reduction reactions in acid medium

Chemiluminescence quantum yields for the reactions of permanganate with oxalic, tartaric, and citric acids; hydrazine; KBr; and FeSO₄ in aqueous solutions of sulfuric acid have been measured. The maximum quantum yield reaches 1.2 × 10^?5 einstein/mol with the chemiexcitation yield being 2%. Hence, the relatively low chemiluminescence quantum yield is due to a low yield of light emission by chemiexcited particles, rather than the low chemiexcitation yield.     

Regularities of the photodestruction of acridine dyes in aqueous media

Acridine dyes were found to exhibit a low light fastness in oxygen-containing aqueous solutions because of photooxidation with the participation of molecular oxygen. The values of the quantum yield for the photooxidation of Acridine Yellow, Acridine Orange, and proflavin acetate at their initial concentration 2 × 10^?5 mol/l were determined to be 1.8 × 10^?3, 1.5 × 10^?3, and 0.8 × 10^?3, respectively. It was concluded that the photooxidation of these acridine dyes in dilute solutions results in the formation of primary photoproducts of peroxide nature. For proflav in acetate, as an example, it was demonstrated that the increase of the substrate concentration to 6 × 10^?4 mol/l results in a fourfold increase in the quantum yield, a behavior indicative of a change in the photodecomposition mechanism. The rate of the interaction between exited and unexcited proflavin molecules, the process responsible for the photodecomposition of this compound, was found to be ～4 × 10⁷ l/(mol s). The quantum yield for the photooxidation of the proflavin base was estimated to exceed that for the photooxidation of the proflavin monocation by more than an order of magnitude.     

Determination of Genistein by Flow‐injection Chemiluminescence Method Based on Ferricyanide Oxidation Sensitized by Rhodamine 6G

A novel flow injection chemiluminescence (FI‐CL) method for the determination of genistein was described. The method was based on the reaction between genistein and potassium ferricyanide in alkaline solution to give weak CL signal, which was dramatically enhanced by rhodamine 6G (Rh G). The CL emission allowed quantitation of genistein concentration in the range 1.0 × 10^?7–4.0 × 10^?5 mol/L with a detection limit (3σ) of 4.2 × 10^?8 mol/L. The relative standard deviation for 11 parallel measurements of 5.0 × 10^?7 mol/L, 4.0 × 10^?6 mol/L and 1.0 × 10^?5 mol/L genistein were 2.59%, 2.40% and 1.48%, respectively. The experimental conditions for the CL reaction were optimized and the possible reaction mechanism was discussed. The method was applied to the determination of genistein in biological fluids.     

A Chemiluminescence Reaction Between Hydroxyl Radical and Rhodamine 6G and its Applications

Abstract

A novel chemiluminescence (CL) reaction between hydroxyl radical and ascorbic acid is described in this paper. Hydroxyl radical generated on line by the reaction between Fe³⁺ solution and H₂O₂ solution in HCl medium could oxidize rhodamine 6G to produce weak chemiluminescence. It was found that ascorbic acid could enhance the chemiluminescence and the excited rhodamine 6G was the emitter of the chemiluminescence reaction. The possible mechanism of the CL system was also discussed. Ascorbic acid can be determined in the range of 2.0×10^?6?8.0×10^?4 mg/ml with a detection limit of 1×10^?6 mg/ml (3σ). A complete analysis could be done in 1 minute with the relative standard deviation of 3.1% for 5.0×10^?5 mg/ml (n=11). In order to study the chemiluminescence reaction further, the application to the determination of ascorbic acid in food using the chemiluminescence reaction combined with flow injection is investigated.     

Determination of Tryptophan in Pharmaceutical Formulations Using a Sequential Injection–Zone Fluidic–Chemiluminescence Tubular Reactor

Tryptophan is an important amino acid for humans with a significant role in cell metabolism. Depletion of tryptophan in the human body may contribute to diseases and development of disorders among the human population. It is, therefore, very important to have a reliable, stable, sustainable, and cost-effective analytical method for the determination of tryptophan. Tryptophan was determined using sequential injection–zone fluidics analysis with luminol–hydrogen peroxide and the Firefly with its unique liquid core waveguide flow-cell design as chemiluminescence tubular reactor with a high-sensitivity photomultiplier tube. This was based on an intense chemiluminescence formation of tryptophan in luminol–hydrogen peroxide inside the tubular reactor for measurement. The chemiluminescence intensity was linear with tryptophan in the range of 1.0?×?10^?6 to 1.0?×?10^?3?mol/L, and the limit of detection was 7.5?×?10^?7?mol/L. The precision for the method was 3.6% (relative standard deviation) for six measurements of 1.0?×?10^?4?mol/L tryptophan. The proposed method has been used to determine tryptophan in pharmaceutical formulations. The system is relatively fast for online assays. Eighty seconds are required to complete one cycle providing a throughput of 45 samples/h. The proposed sequential injection analysis–zone fluidics–chemiluminescence system for the assay of tryptophan in certain specific pharmaceutical capsules is simple, reliable, sustainable, and convenient with relatively low-cost consumption of reagents.     

Determination of Diammonium Glycyrrhizinate and Its Antioxidant Activity Using a Novel Chemiluminescence System

A novel chemiluminescence (CL) system was established for the determination of diammonium glycyrrhizinate (DG) in pharmaceutical preparations and its ability of scavenging hydroxyl radical. It was shown that a strong CL signal was observed when Eosin Y mixed with Fenton reagent. The CL intensity was decreased significantly when DG was added to the reaction system and partially scavenged the hydroxyl radicals in the solution. The extent of decrease in the CL intensity had a good stoichiometrical relationship with DG concentration. Based on this, we developed a new method for the determination of DG using a flow injection chemiluminescence (FI-CL) technique. Under the optimal conditions, the linear range of DG concentration was 6.0 × 10^?8–5.0 × 10^?6 mol/L (R = 0.9982) with a detection limit of 8.0 × 10^?9 mol/L (SN = 3), and the RSD was 3.8% for 2.0 × 10^?7 mol/L DG (n = 11). This method was successfully used in the determination of DG in tablets and the evaluation of hydroxyl radical scavenging capacity of DG. The possible reaction mechanism of the CL system is discussed.     

Graphene quantum dot-phthalocyanine polystyrene conjugate embedded in asymmetric polymer membranes for photocatalytic oxidation of 4-chlorophenol

The feasibility of using π–π stacking as a means of fixing unsubstituted Zn phthalocyanine (ZnPc) to a support prior to formation of photoactive polymer asymmetric membranes was explored. Stable ZnPc–graphene quantum dot-polystyrene conjugates (6.15 μmol/g ZnPc loading) were synthesized and embedded in polystyrene membranes which proved to be photoactive with a singlet oxygen quantum yield of 0.43 in ethanol and 0.37 in water. The membranes also proved to be active in the photocatalytic oxidation of 4-chlorophenol in water where the reaction followed second-order kinetics. At 3.24 × 10^?4 mol L^?1, the photo-oxidation of 4-chlorophenol was observed with a k_obs of 35.9 L mol^?1 min^?1 and a half-life of 86 min.     

Flow-Injection Chemiluminescent Determination of Piroxicam Using Tris (2,2′-bipyridyl) Ruthenium(II)—Potassium Permanganate System

Abstract

A rapid and sensitive chemiluminescence method using flow-injection has been developed for the determination of an analgesic agent drug, piroxicam. The method is based on the chemiluminescence reaction of piroxicam with an acidic potassium permanganate and Ru(bipy)₃ ²⁺. The chemiluminescence intensity is greatly enhanced when quinine sulfate is used as a sensitizer. After optimization of the different experimental parameters, a calibration graph was obtained over a concentration range of 3.0 × 0^?8–3.0 × 0^?5 mol L^?1 with the detection limit of 1.0 × 0^?8 mol L^?1. The relative standard deviation is 1.5% (n = 11) for the determination of 8.0 × 10^?7 mol L^?1 piroxicam. The proposed method was successfully applied to commercial tablets, spiked serum, and urine samples.     

Molecular Imprinting-Chemiluminescence Sensor for the Determination of Prulifloxacin

Abstract

A selective molecular imprinting-chemiluminescence sensor is developed for the determination of prulifloxacin by using a prulifloxacin-imprinted polymer as recognition material and the cerium(IV)/sodium thiosulfate/prulifloxacin chemiluminescence reaction as the detection system. The linear response range of the sensor is from 8.0 × 10^?8 to 7.0 × 10^?6 mol L^?1 with a detection limit of 2.0 × 10^?8 mol L^?1. The relative standard deviation for 5.0 × 10^?7 mol L^?1prulifloxacin solution is 1.3% (n = 7). This sensor has been applied to the determination of prulifloxacin in urine samples, and the results obtained are satisfactory.     

Flow Injection Chemiluminescence Determination of Puerarin in Pharmaceutical Preparations Using Eosin Y‐Fenton System

A novel chemiluminescence (CL) system was established for the determination of puerarin in pharmaceutical preparations. It was shown that a strong CL signal was observed when Eosin Y reacted with the hydroxyl radicals which were generated from Fenton reagent in acidic medium. The CL intensity was decreased significantly when puerarin was added to the reaction system and partially scavenged the hydroxyl radicals in the solution. The extent of decrease in the CL intensity had a good stoichiometrical relationship with puerarin concentration. Based on this, a new method for the determination of puerarin using a flow injection chemiluminescence technique was developed. The experimental parameters that affected the CL intensity were optimized. Under the optimal conditions, the linear range for puerarin concentration was 8.0×10^?8?2.0×10^?6 mol/L (R=0.9982) with a detection limit of 7.5×10^?9 mol/L (S/N=3) and the relative standard deviation was 1.7% for 4.0×10^?7 mol/L puerarin (n=11). The proposed method was applied to the determination of puerarin in a puerarin injection with satisfactory results.     

Flow‐Injection Chemiluminometric Analysis of Thyroxine Hormone in a KMnO,4‐Na2SO3 System

An analytical method consisting of flow injection sampling and chemiluminescence detection for the determination of thyroxine hormone is described. It is based on the weak chemiluminescent reaction of KMnO₄ ‐ Na₂SO₃ in acidic medium, which is enhanced by the addition of thyroxine hormone. The chemiluminescence intensity was correlated linearly with concentration of thyroxine in the range of 1.0 × 10^?7 – 2.0 × 10^?6 mol L^?1 (r² = 0.9976) with a relative standard deviation (n = 4) in the range of 1.0 – 1.9%. The limit of detection (3σ blank) is 5.0 × 10^?9 mol L^?1 with a sample throughput of 180 h^?1. The method has been applied to the determination of thyroxine in pharmaceutical preparations and the results are in good agreement with the value reported. Metal and non‐metal ions and some organic compounds commonly present in tablets and some amino acids were also studied for thyroxine determination.     

One‐Pot Synthesis of CdSe Quantum Dots in Aqueous Solution for Biological Labeling

The one‐pot synthesis of water‐soluble and biologically compatible yellow CdSe quantum dots (QDs) featuring the use of glutathione (GSH) as the capping and reducing agent was achieved under aqueous conditions at 150 °C. The synthesized yellow CdSe QDs with quantum yield (QY) up to 20% exhibit zinc blende cubic structure particles with an average diameter of 4‐5 nm. It was found that both molar ratio of Se/Cd and reaction time had a significant effect on size distribution of GSH‐CdSe QDs. Meanwhile, the interaction of QDs bioconjugated to bovine hemoglobin (BHb) was studied by absorption and fluorescence(FL) spectra. With addition of BHb, the FL intensity of CdSe QDs largely quenched due to the static mechanism. The linear range is 5.0 × 10^?8 mol/L to 3.0 × 10^?6 mol/L, and the correlation coefficient is 0.9991, suggesting that could be used as a probe to label biological molecules and bacterial cells.     

An Ultrasensitive Analytical Method Based on Chemiluminescence Sensing Electrochemical Parallel Catalytic Reaction Event

An ultrasensitive electrochemiluminescence (ECL) method on the combination of electrochemical parallel catalytic reaction and chemiluminesence signal sensing was proposed for improving ECL analytical characteristics using vanadate(V) as a representative. Vanadate(V) could be electrochemically reduced to generate vanadate(II) which could be chemically oxidized by potassium periodate to regenerate vanadate(V) and give parallel catalytic wave effect. Then, the reduced product of potassium periodate could react with butyl‐rhodamine B to emit a sensitive chemiluminescence signal. The chemiluminescence intensity was correlative with vanadate(V) concentration. The investigation on the electrochemical reaction rate constant (k⁰) confirmed that the speed of electrochemical reaction was faster than that of the subsequent chemiluminescence reaction. The possibility of the combination of electrochemical parallel catalytic reaction with chemiluminescence signal sensing was proved. The similar ECL behaviors could be observed at zirconia nanowires‐Nafion modified electrode. Because of the separation and enrichment effect of the modified electrode on vanadate(V), the selectivity and sensitivity was further improved greatly. Based on these findings, a new concept on the combination of electrochemical parallel catalytic reaction and chemiluminesence signal sensing was proposed and an ultrasensitive ECL method for the determination of vanadate(V) was developed at zirconia nanowires‐Nafion modified electrode. Under the optimum experimental conditions, the ECL intensity was linear with the concentration of vanadate(V) in the range of 2.0×10^?12 mol/L–2.0×10^?10 mol/L. The detection limit was 8.0×10^?13 mol/L, which was more than 6 orders of magnitude lower than that observed by electrochemical current transduction for electrochemical parallel catalytic reaction at zirconia nanowires‐Nafion modified electrode.     

Direct chemiluminescence determination of fenbufen by the enhancement of the {\text{Ru}}\left( {{\text{phen}}} \right)_3^{2 + } –cerium(IV) system

A method is described for determination of fenbufen that is based on the chemiluminescence (CL) reaction of the ${\text{Ru}}\left( {{\text{phen}}} \right)_3^{2 + } $ –cerium(IV)–fenbufen system. An enhanced CL reaction was developed, and optimum conditions for CL were investigated. The CL was linearly dependent on fenbufen concentration in the range 4.0?×?10^?8–9.0?×?10^?6 mol L^?1. The detection limit was 2.0?×?10^?8 mol L^?1. The relative standard deviation (RSD) was 2.8% for eleven measurements of 6.0?×?10^?7 mol L^?1 fenbufen standard solution. The new method enables simple, sensitive, and rapid determination of fenbufen and has been used for determination of fenbufen in pharmaceutical preparations in capsule, spiked serum and urine samples.     

Involvement of ·OH radicals in the mechanism of excitation of the uranyl ion in the chemiluminescent oxidation of U(IV) by atmospheric oxygen in aqueous solutions of perchloric acid

The chemiluminescence (CL) kinetics in U(IV) oxidation by atmospheric oxygen in aqueous HClO₄ has been investigated. The CL quantum yield (η_CL, E/(mol U(IV))) in this reaction is 1.4 × 10^?8. The elementary event generating the CL emitter, which is the electronically excited uranyl ion *(UO ₂ ²⁺ ), is electron transfer from the uranyl ion UO ₂ ⁺ to the oxidizer (^·OH radical). The Ag⁺ ion quenches CL, and the Cu²⁺ ion enhances CL.     

Lower photoreactivity of 3-methyl-3-(4′-biphenylyl)-t-butene

Direct and sensitized photolyses of 3-methyl-3-(4′-biphenylyl)-1-butene gave 1,1-dimethyl-2-(4′-biphenylyl)cyclopropane as primary product and 2-methyl-4-(4′-biphenylyl)-1-butene as secondary product with quantum yields of 7.6×10^?3 and 5.6×10^?3, respectively. On direct photolysis, the triplet reactant rearranged with a quantum yield of 4.4×10^?3 and is more reactive than the singlet. The exceptionally low photoreactivity shows that the excitation energy is largely localized on the biphenylyl portion but can be delivered to the reaction center slowly.     

Peroxide optrode based on micellar-mediated chemiluminescence reaction of luminol

Cetyltrimethylammonium bromide (CTAB) was used to overcome the pH mismatch of the luminol (5-amino-2,3-dihydrophthalazine-1,4-dione ) chemiluminescence reaction when coupled to the glucose/glucose oxidase reaction at neutral pH. The results demonstrate the feasibility of conducting both reactions simultaneously and efficiently at pH 7.5–8.5. The incorporation of the CTAB micellar system in the coupled luminol/enzymatic reaction allows quantification of glucose in the 3 × 10^?7?3 × 10^?4 M range. The relative standard deviation (RSD) for 5 replicates of 5 × 10^?5 M glucose was 3.8%. Also, hydrogen peroxide was quantified in the 1.2 × 10^?4?2.4 × 10^?8 M range with RSD 2.6%. The micellar-mediated luminol reaction was applied successfully to the determination of glucose in blood serum. Excellent agreement with reported results by standard assays was obtained.     

Flow Injection Chemiluminescence Determination of Phenol in Neutral Medium

A new flow injection chemiluminescence method for the determination of phenol was proposed, based upon the chemiluminescence reaction of phenol, N-bromosuccinimide, and hydrogen peroxide in neutral aqueous medium in the presence of cetyltrimethylammonium bromide surfactant micelles. The chemiluminescence signal was proportional to the concentration of phenol in the range of 1.0 × 10^?7?8.0 × 10^?6 g/mL with a detection limit of 3 × 10^?8 g/mL. The relative standard deviation for 1.0 × 10^?6 g/mL phenol solution was 2.0% (n = 11). The proposed method was successfully applied to the determination of phenol in phenol ear drops. A possible CL reaction mechanism was also discussed briefly.     

Determination of Albumin Using the Chemiluminescence of Tb3+/K2S2O8 System

A new chemiluminescence system of Tb³⁺/K₂S₂O₈ was developed for the determination of albumin. Some experimental conditions were examined and optimized. The linear ranges of the calibration curves are 5.0 × 10^?9–5.0 × 10^?6 mol/L for bovine serum albumin, 5.0 × 10^?8–1.0 × 10^?5 mol/L for human serum albumin and 2.5 × 10^?7–1.0 × 10^?5 mol/L for ovalbumin, and the corresponding detection limits are 1.9 × 10^?9 mol/L, 1.5 × 10^?8 mol/L, and 1.5 × 10^?7 mol/L, respectively. The method was applied to the determination of albumin in human serum samples, and the results were in agreement with those obtained by the bromcresol green method. The relative errors for the analytical results were from ?2.0% to 4.3%.     

Study on Diffusion Mechanisms and Determination of Dihydroxybenzene Isomers at the Pre‐anodized Inlaying Ultrathin Carbon Paste Electrode

In this paper, nichrome was adopted as a substrate, to fabricate the pre‐anodized inlaying ultrathin carbon paste electrode (PAIUCPE). The electrochemical behaviors and diffusion mechanisms of three dihydroxybenzene isomers at the electrode were carefully investigated. The effect of pH on oxidation peak current was also detailedly explained. The results were shown that oxidation peak current not only related to the reaction of electroactive materials at the working electrode, but also depended on the reaction variable of reduction at the auxiliary electrode. The oxidation peaks of hydroquinone (HQ), catechol (CC) and resorcinol (RC) located at 0.181 V, 0.288 V and 0.736 V. For CC, RC and HQ, the oxidation peak currents were linear to the concentrations at the range of 5.0 × 10^?6～5.0 × 10^?4 mol/L, 3.0 × 10^?6～5.0 × 10^?4 mol/L and 4.0 × 10^?6～4.0 × 10^?4 mol/L with the detection limits of 2.0 × 10^?7 mol/L, 1.2 × 10^?7 mol/L and 1.2 × 10^?7 mol/L, respectively. The proposed method was successfully applied in the simultaneous determination of dihydroxybenzene isomers in artificial sewage samples with satisfactory results.